Rotary transformer.



"Nu. 708,025. Patented Sept 2, I902.

A. CHUBCHWARD.

ROTARY TRANSFORMER.

(Application filed June 12, 1899.)

(N0 Mudel.)

UNITED STATES PATENT OFFICE.

ALEXANDER CHURCHWARD, OF CHICAGO, ILLINOIS.

ROTARY TRANSFORMER.

SPECIFICATION forming part of Letters Patent No. 708,025, datedSeptember 2, 1902.

Application filed June 12,1899.

To all whom it may concern:

Be it known that I, ALEXANDER CHURCH- WARD, of Chicago, in the county ofCook and State of Illinois, have invented certain new and usefulImprovements in'Rotary Transformers, of which the following isaspecification.

This invention relates to rotary transformers for changing alternatingelectric currents to continuous currents,or vice versa,by means of arotary armature the coils of which are connected both in the alternatingcircuit or circuits by collector-rings and in the continuouscurrentcircuit through acommutator; and it relates more particularly toimprovements in that class of such rotary transformers as areconstructed and used for polyphase-current work. In such machines asheretofore constructed the armatures have customarily been of thesingle-winding type-4. a, the armature has had butone winding,which wastapped off at the necessary intervals to give the required phasedifferences, accordingly as the apparatus was used in a single, two, orthree phase system. The objection to this construction in a polyphasemachine is that the phases are thereby interconnected, so that anyirregularity or change in either will react on the others through theircommon armature-winding and render it difficult or impossible to operatesuccessfully if the phases are unbalanced or to run satisfactorily withthe remaining phase or phases if one phase fails. Furthermore, unlessthe system is carefully balanced, as is frequently impossible on longtransmission-lines, there is liable to be excessive flashing or sparkingat the commutator, owing to the comparatively high voltage between thecommutator-bars. To avoid these objections, my invention contemplatesthe provision on the armature of a separate winding and separatecollector-rings and a set of commutatorbars for each phase. For example,in a twophase machine I provide two separate windings which may beplaced in the same slots, each having half the cross-section of copperwhich would be used for a single winding for the same machine, so thatthe quantity of copper is approximately the same in both cases. Each ofthese windings is thencon- Serial No. 720,156. (No model.)

nected with a separate pair of collector-rings and with a separate setof commutator-bars which may be combined in a single commutator or maybe divided into separate oomm utators, as found desirable. In eithercase the phases may be regulated independently of each other and neitherwill be affected by any alteration in or cessation of the other.Moreover, the provision of two sets of commutator-bars greatly reducesthe voltage between the bars and the likelihood of flashing or sparkingat the brushes.

The invention consists in the matters herein set forth, and particularlypointed out in the appended claims, and will be fully understood whenconsidered in connection with the accompanying drawings, in which Figurel is a diagrammatic view showing the windings and connections of thearmature of a transformer designed in accordance with myinvention. Fig.2 isa somewhat diagram.- matic representation of an armature which isalso constructed in accordance with the invention, but provided with twocommutators instead of one, as in the first diagram.

As shown in Fig. 1, Adesignates the armature, representeddiagrammatically, of a rotary transformer designed for a two-phasesystem of transmission, a a collector-rings which are connected in thecircuit 1 of the two-phase system, and tr e collector-rings which areconnected in the other circuit 2 of said system. In accordance with myinvention said armature is provided with two separate windings A and Aof which the firstis connected by suitable taps with the collectorringsa a, while the second is connected with the collector-rings a a. Eachwinding consists of any desired number of coils connected in series toeach other and also suitably connected with the bars of the commutatorA, as shown, a different set of commutator-bars being, however, providedfor each of the two separate windings A and A Commutatorbrushes B thentransmit the current to the leads I) of the continuous-currentcircuit.Having no com mon winding, the phases in this construction areindependent of each other, so that variations or changes in the one donot directly affect the other or prevent either from being independentlyadjusted. The two separate windings, furthermore, permit of theprovision of double the number of commutator-bars without encroachingupon the 5 limits imposed by considerations of frequency,

IO that the two sets of commutator-bars be combined in a singlecommutator, as in the construction thus described and illustrated inFig. 1; but they may be divided into separate commutators, from whichbrushes B and B transmit the current to the leads 1) and b,

which may form independent continuous-current circuits or may beconnected in series or multiple, as desired.

Although thus described in connection with a two-phase machine, it willbe understood that the same principles of construction will apply torotary transformers designed to work in three or more phase systems, inwhich cases three or more separate windings and pairs of collector-ringsand three or more times the number of commutator-bars would be provided,with a corresponding advantage in the matter of regulation of thedifierent phases and in the commutation and lessening of the tendencytoward fiashin g and sparking.

I claim as my invention- 1. A rotary transformer for multiphase systemsprovided with a plurality of armature- Windings corresponding in numberto the number of phases in the system, a separate pair ofcollector-rings connected with each winding, and a separate set ofcommutatorbars connected with each winding, whereby the phases aremaintained independent of each other.

2. A rotary transformer for multiphase systems provided with a pluralityof armaturewindings corresponding in number to the number of phases ofthe system, a separate pair of collector-rings connected with eachwinding, and a separate commutator for each Winding.

In testimony that I claim the foregoing as my invention I affix mysignature, in presence of two subscribing witnesses, this 6th day ofJune, A. D. 1899.

ALEXANDER OHURCHWAR D.

Witnesses:

HENRY W. CARTER, ALBERT H. GRAVES.

